Tarantula: A Surprising Spider
By GARY ROBBINS, The Orange County Register

A showy species of tarantula that some people keep as pets spins silk not only from its abdomen but its feet as well, a discovery that startled the scientists from UC Irvine and Germany who figured it out.

"We were floored," said Adam Summers, an evolutionary biologist at UCI. "Everyone knows that spiders spin silk from spinnerets on their hind-ends (abdomen area). But we had no idea that this charismatic spider (the zebra tarantula of Costa Rica) also could do it with their feet."

Summers say the tarantulas produce a gluey, adhesive form of silk that comes out of spigots in the toes of the animal's eight legs. The silk is one-tenth the width of a human hair, making it hard to see and study.

The new discovery, reported Wednesday in the journal Nature, raises a subtle but interesting question in evolutionary biology: did the tarantula first spin silk from their abdomens? Or did they first spin from their feet to help with traction?

"We're wondering how we missed this," Summers said. "A tarantula in the palm of your hand is as big as a golf ball. You'd think we would have known is."

In a news release, UCI and Summers said many spiders "can produce seven different kinds of silk. Scientists will look at the genes involved in silk production from the feet, compare them to the gene family that leads to spinneret silk production, and be able to better determine whether silk was originally used for traction, or whether that was a secondary usage that came later."